使用 C# 中的 NEST 库调用 elasticsearch 时，如何向 linq 语句添加条件逻辑？

Posted 2023-03-30

【中文标题】使用 C# 中的 NEST 库调用 elasticsearch 时，如何向 linq 语句添加条件逻辑？

【英文标题】：How to add conditional logic to a linq statement when calling elasticsearch using the NEST library in C#?

【发布时间】：2021-07-28 17:13:13

【问题描述】：

我正在尝试在 C# 中使用流利的 LINQ 来使用 .NET NEST library 查询 Elasticsearch 服务器。

我想根据传入的搜索请求构建 LINQ 语句。如果搜索请求有价格范围，我想在 Elasticsearch 请求中添加一个范围子句。这是我的代码

var products = await client.SearchAsync<Product>(x =>

      x = x.Query(q =>
      
          if (request.IsAvailable.HasValue)
          
               // this gets called, but it is never added to the final elasticsearch call.
              q = q.Match(b => b.Field(bm => bm.IsAvailable).Query(request.IsAvailable.Value ? "true" : "false")) as QueryContainerDescriptor<Product>;
          

          if (request.MinPrice.HasValue || request.MaxPrice.HasValue)
          
              // this gets called, but it is never added to the final elasticsearch call.
              q = q.Range(r =>
              
                  if (request.MinPrice.HasValue)
                  
                      r = r.Field(x => x.Price).GreaterThanOrEquals(request.MinPrice.Value);
                  

                  if (request.MaxPrice.HasValue)
                  
                      r = r.Field(x => x.Price).LessThanOrEquals(request.MaxPrice.Value);
                  
                  return r;
              ) as QueryContainerDescriptor<Product>;
          

          if (request.Types != null && request.Types.Length > 0)
          
              // this gets called, but it is never added to the final elasticsearch call.
              q = q.Terms(t => t.Field(f => f.Type).Terms(request.Types)) as QueryContainerDescriptor<Product>;
          

          return q;
      );

      x = x.Source(s => s.Excludes(se =>
      
          // This works! There fields are being excluded as expected
          if (request.ExcludeSummary)
          
              se = se.Field(sef => sef.Summary);
          

          if (request.ExcludeTimestamp)
          
              se = se.Field(sef => sef.Timestamp);
          

          if (request.ExcludeLabels)
          
              se = se.Field(sef => sef.Labels);
          

          if (request.ExcludeTags)
          
              se = se.Field(sef => sef.Tags);
          

          return se;
      ));

      return x;
);

Query() 中的所有条件都不会添加到弹性搜索请求中。这意味着生成的 json 请求没有价格或 IsAvaliable 的子句。我怀疑选角是罪魁祸首，但不知道如何解决。

Source() 正在按预期工作。它将正确的字段添加到excludes 列表中。

如何正确地将查询子句添加到Query() 部分？

【参考方案1】：

我发现了这个问题。似乎 NEST 采用了最后一个子句并忽略了所有前面的子句。

这是我为修复它所做的工作

var products = await client.SearchAsync<Product>(x =>

      x = x.Query(q =>
      
          QueryContainer qc = q;

          if (request.IsAvailable.HasValue)
          
              qc = qc && +q.Match(b => b.Field(bm => bm.IsAvailable).Query(request.IsAvailable.Value ? "true" : "false"));
          

          if (request.MinPrice.HasValue || request.MaxPrice.HasValue)
          
              qc = qc && +q.Range(r =>
              
                  if (request.MinPrice.HasValue)
                  
                      r = r.Field(x => x.Price).GreaterThanOrEquals(request.MinPrice.Value);
                  

                  if (request.MaxPrice.HasValue)
                  
                      r = r.Field(x => x.Price).LessThanOrEquals(request.MaxPrice.Value);
                  
                  return r;
              );
          

          if (request.Types != null && request.Types.Length > 0)
          
              qc = qc && +q.Terms(t => t.Field(f => f.Type).Terms(request.Types));
          

          return qc;
      );

      x = x.Source(s => s.Excludes(se =>
      
          if (request.ExcludeSummary)
          
              se = se.Field(sef => sef.Summary);
          

          if (request.ExcludeTimestamp)
          
              se = se.Field(sef => sef.Timestamp);
          

          if (request.ExcludeLabels)
          
              se = se.Field(sef => sef.Labels);
          

          if (request.ExcludeTags)
          
              se = se.Field(sef => sef.Tags);
          

          return se;
      ));

      return x;
);

【讨论】：

很高兴看到您找到了解决方案。还描述了使用&& 运算符组合查询here in the documentation